CD8 T lymphocytes respond to epitopes (protein segments attached to MHC-I molecules) expressed on the cell membrane. If there is foreign DNA merged with the host DNA in the cell nucleus (e.g. from a retrovirus), this may be transcribed into RNA segments and translated into foreign proteins. Peptides from these proteins will be presented on MHC I molecules on the cell membrane. CD8 T lymphocytes that are specific to this MHC-I - peptide complex recognise the cell as infected. So, indirectly, CD8 T cells can in principle detect foreign DNA. However, this approach has been tried in HIV vaccines without success. In fact, there is no CD8 T cell vaccine yet, although there is extensive research.

Dear Janka,

Thanks for such a comprehensive reply. But, in this case, in my opinion, CD 8 T lymphocytes can not detect the DNA, as this entirely depends upon translation of the DNA

You are absolutely right. If transcription is not activated (as in HIV latency), foreign DNA cannot be detected.